Exploration of data space through trans-dimensional sampling: A case study of 4D seismics
Description
Data repository in the article: "Exploration of data space through trans-dimensional sampling: A case study of 4D seismics" submitted to JGR: Solid Earth. We consider a simple time-lapse scenario that consists of an overburden layer and a reservoir. To better mimic a real world application, we use a scaling factor of 10000 such that a frequency of 200 kHz represents a frequency of 20 Hz, and a dimension of 1 mm represents 10 m. To build this experiment in the lab we take two Plexiglas blocks with dimensions 310 x 154 x 77 mm, and attach them together. The first Plexiglas block represents the overburden layer with elastic properties of Vp = 2780 m/s, Vs = 1480 m/s, and rho = 1.19 g/cm3. This overburden layer remains unchanged between the two surveys. To build the reservoir layer we remove a rectangular cube from the second block, allowing us to insert different fluids into our "reservoir". For the baseline survey, we keep the second block empty, representing a gas-filled reservoir. In this case, the elastic properties of the air are Vp = 332 m/s, V_s = N/A, and rho ~ 0 g/cm3. For the monitor survey, we fill the block with water, miming a scenario where the gas in the reservoir has been replaced with brine. The elastic properties of the water are Vp = 1500 m/s, Vs = N/A, rho ~ 1 g/cm3. For the source we use a P-wave transducer with a single-cycle sine wavelet at 200 kHz, generated through the function generator. This P-wave transducer has a diameter of 10~mm. For the receivers, we use a laser vibrometer that measures the particle velocity along the direction of the laser beam (perpendicular to the surface), and sends it to the oscilloscope to be saved. The laser measures the signal at 160 points along the tape, giving us a total of 160 receivers with a sampling distance of 0.5 mm. The nearest offset in this case is 10 mm. Throughout the data acquisition the P-wave transducer is glued to the Plexiglas box, and the laser is attached to a stage that stably moves it along the tape. This allows for a controlled and repeatable time-lapse experiment. Summarising, the experimental set-up allows us to record 160 "wiggles" for each of the two different reservoir-states, composing two "shot-gathers". Directories contains the 160 wiggles recorded during the two different experiments